1. Field of the Invention
The present invention relates to an image processing controller and an image forming apparatus.
2. Description of the Related Art
An image forming apparatus such as a printer and a copying machine generally includes a controller application-specific integrated circuit (ASIC) that is operative to connect an engine unit to a central processing unit (CPU) and performs image forming processing by the CPU. Specifically, the controller ASIC and the engine unit are connected to each other via a bus, such as a peripheral component interconnect (PCI) interface (I/F), and the controller ASIC is also connected to the CPU, so that processing such as printing processing and copying processing is performed under the control of the CPU. The CPU is generally connected to the controller ASIC with a chipset because what an interface a CPU employs is not disclosed. Therefore, the CPU is connected to the chipset with the PCI I/F.
A performance of the image forming apparatus depends on a data transmission speed of the PCI I/F. However, the performance of the PCI I/F run with the chipset is generally relatively low, degrading the performance of the image forming apparatus.
A PCI-EXPRESS I/F with a capability of performing data transmission at a transmission speed higher than that of the PCI I/F is increasingly in practical use. By employing the PCI-EXPRESS I/F, the performance of the image forming apparatus can be enhanced.
A conventional image forming apparatus in which the controller ASIC is connected to the engine unit with a PCI I/F, and the controller ASIC is connected to the CPU with a chipset is disclosed in Japanese Patent Application Laid-open No. 2003-309680.
For using the PCI-EXPRESS I/F, a PCI-EXPRESS root complex controller and a PCI-EXPRESS endpoint controller having the PCI-EXPRESS I/F need to be installed in the controller ASIC. However, if the controller ASIC is provided only with the controllers having the PCI-EXPRESS I/F without a PCI controller having a PCI I/F, an engine such as a scanner and a plotter employing the PCI I/F cannot be used with the controller ASIC. Thus, it is preferable to install both the PCI-EXPRESS I/F and the PCI I/F to enhance usability of the image forming apparatus. To provide the controller ASIC with both the PCI-EXPRESS I/F and the PCI I/F, it is necessary to control data transmission path in the controller ASIC; however, such a technology has not been known.